US2499425A

US2499425A - Control valve for double-acting hydraulic systems

Info

Publication number: US2499425A
Authority: US
Inventors: William T Stephens
Original assignee: HYDRAULIC EQUIPMENT Co
Current assignee: HYDRAULIC EQUIPMENT Co
Priority date: 1944-08-18
Filing date: 1948-09-03
Publication date: 1950-03-07
Anticipated expiration: 1967-03-07

Description

March 7, 1950 w. T.- STEPHENS CONTROL VALVE FOR DOUBLE-ACTING HYDRAULIG SYSTEMS 2 sheets-sheet 1 Original Filed Aug. 18, 1944 @WH m .HWHOQ mm 1w HQ Ham om OHH N0 375B NR l March 7, 1950 w; T. STEPHENS CONTROL VALVE FOR DOUBLE-ACTING HYDRAULIC SYSTEMS Original Filed Aug 1 1944:

2 Sheets-Sheet 2 Patented Mar. 7, 1950 "HYDRAULIC SYSTEMS "William "1. Stephens, Pa'i'nesville, Ohio, assignor, by mesne assignments, to flydraulic Equipment "Company, Cleveland,

Ohio, a corporation --'of Oriwinal lapplieation August 18,, .1944, Serial N0.

her .3, 1948,

'olosedtype to insure againstundesired movement of the hoist, on its lowering operati'on, due to the action of the load and independent of the rate of supply of the 'liquidcausing the loweringoperation.

As animp'ortant ieatunel of the invention there is provided means for-operating the -system inthe closed manner-during movements of the hoistin either direction :and for automatically converting to the open-system at =a11 other times.

A further important fea'ture or the invention resides in the provision of a flow control valve for use with closed-systems whieh not only -provides for the automatic :conversion 150 the op en system when hoisting is not taking place, bu't which provides for an "adequate supply -of -l-iquid to the :pump (inlet under an 1 conditions and for relief of excess liquid in the easeof difierential volumes becoming- -avail-abl'e trom th'e two ends of the hoist.

Among the essential features of which contribute to-its: simplicity of construction and operation is theinc'orp'or'ation in the'manua'l i control valve of a single check valve autom-atically 'operable on both hoistingandrlowering 10perati'ons to insure against return offfluid from the hoist toward the pump.

rO'ther Jfeatures and objects f the invention include the. simplicity of the valve lhousing' structune, the arrangement and disposition of the main and auxiliaryvalve partsfthe construction of the valve-plungers,"their ports and pa'ssages, and means providing for handling differential volumes of 'fluid-from the two 'ends 'o'f the ho'i'st when the control valve is in :the moat position.

= Other and further objects 'and features oi the invention will be more apparent to those skilled in the art upon a consideration of the-accompanying drawings and the following specification wherein are disclosed several exemplary einbodi merits of f the invention, it being understood that such ichanges, modifications fanil icombinationssof the several :figures may :bermade mill 6 Claims. (Cl. "27 72-203 -nowiBatent.l lo. 2,477,669, dated August this application Septem- I the scope of the appended :claims :withoutiiepanh the invention ing from :the spirit oihthe invention.

In said drawings: Figure 1 is a schematic-and diagnammaiticmeps resentationof a hydraulic :controlsystem Ifor :the operation oi -a double acting-hoist lor ram byithe so-called closed-circuitsystem; Figure 2 is .a ilong itudin'al .uc'entral section I through :a control-valveadapted :ior lose :with a system of the type illustrated .iniEigure ;1:; and

Figure $18 ea longitudin'al :centtal section through. a 1 control valve :ior 'lu-se in a 'closed system of :theityp'e illustrated in digute 1, the waive representing .:a simplification of "the constnuotion illustratediinaFigu-irez.

:In the .:operation .of double .zactin zhydraul-ic devices such ;as vexams, hoists and the dike, iiconclitions :aris'e, r dependent-iupon iconnecte d mechanical e'apparatus, necessitating .extremely accurate control of the position of the piston, togethen'with some #means -"to prevent :movement *of ithe piston :out of controlxof ."the hydraulicdiquid as,;ior.=instance, under the operation -.or Weight of vIth'e load when the lattersis :beingl'lowesed.

The present-invention deals primarily with a valve intended .for the nontitol :of the Zihydnaulic .cylinderzor'shoist:usedffor the manipulation :oi the blade son-a *zbulldozer or grader, but :is snot to :be :construed. as :so limited. since it is lcapablexof use in-.=a widewariety of z fields. The-description, .IhOW-e ever, for the sake of convenience, willareierstoithe preferreduse :of the apparatus.

.;In "the operation not a ihu'lld'ozer for lgnading 'orasimilar earth handlingnnanipulations,:itziscalee sired that the blade may beraiseol, held, lowered .orzpermitted to float, underLtheainstantrandeaccue rate control of .thecopenator. Difficulties have 'henetofore beeniexperienced Bin equipmentiof this sort wheniattempts weremade to lower the blade. ats considerable weight stends to withdraw the piston vlf rom the :liquid following it and intended to regulate its rate aof lowering ion. release :of the liquid supporting '--the piston. This provides zen- :ratic l'operation :and :prevents the :attainment cof the fine cgrading which can be achieved ;.with machines of this type-gprovided with proper-eontrols. i Heretoionetwo :general systemszhave ibetenzus'ed lin-aa'naendeavor to overcome' the -above'mentioned .diffieulty. :Eihesfirst .oftheseis-the use :of the-so- .ealled closed system wherein-the positive dis placement-pump ifor rcirculating :the ipressure aliqau'i'dis connected to .reeeiveits :supplvof diguid from-lone .end of .theg-hoist cylinder-while deliver mg to "the :opposite end. prevents-lumen,

trolled travel of the piston under the weight of the blade since liquid is withdrawn only as fast as delivered, but this system circulates such a small quantity of liquid that overheating is prevalent, particularly in the neutral or hold position, when fluid is merely circulated from the pump to the valve and back. The tank or reservoir serves only to provide reserve liquid and to take care of a differential in displacement at the two ends of the cylinder, one of which is occupied by a piston rod.

In the other or so-called open system, liquid is delivered from the high pressure side of the pump to operate the hoist on the lift stroke and fluid is returned to the tank from the opposite end of the hoist. The pump inlet is from the tank. Upon the lowering stroke some form or flow control valve is provided to limit the rate at which the liquid can be returned to the tank from the hoist in an endeavor to prevent the piston leaving the liquid in the upper side of the cylinder. Such flow control valves have not been wholly satisfactory because they were not constructed to regulate the rate of flow in accordance with the proper requirements. This system is not subject to serious overheating since the pump at all times takes its liquid from the large supply tank where cooling is adequate.

In accordance with the present invention improvements are made in the first system. In the system, operation when hoisting or lowering is in the normal closed system manner with the two ends of the hoist being connected to the two sides of the pump whereby overrunning is prevented. However, in the hold or neutral position, the system is converted automatically to an open one and the pump circulates liquid from and to the tank, thus preventing overheating during by far the longest periods of normal operation.

Material simplification of the valve housing structure is achieved by providing the check valve, which prevents return of high pressure liquid from the cylinder toward the pump, within a bore which is provided longitudinally of and in the valve plunger, which bore likewise permits the high pressurefluid to by-pass certain of the control grooves in the plunger surface between the lands thereon. This singlecheck valve serves when supplying high pressure fiuid to either end of the hoist.

Referring now to Figures 1 and 2 of the drawing, there is illustrated a closed system for hoist operation together with details of a valve for controlling the same. The system of Fig. 1 includes the positive displacement pump IIB, the tank or reservoir IIZ, the valve I I4 and the double acting hoist I25 housing piston I26 having piston rod I2l atone end. The pump is connected directly only to the valve by \pipes 80 and 8I and the tank only to the valve as by

conduits

82 and 83. Opposite ends of the hoist are connected to the valve by lines I29 and I2I respectively. It will be noted that the displacements at the two ends of the hoist cylinder are different and the valve provides means to compensate for this.

Fig. 2 illustrates in detail one form of valve for controlling the system of Fig. 1. Here the housing II 4 is preferably unitary and for the sake of convenience and to reduce the amount of piping and the space occupied by the hydraulic equipment, is arrangedtto be mounted directly on the bottom wall 85 of the tank -I I2. For this purpose the housing top is flat. Corresponding openings in the tank and housing meet to take the place of

pipes

82 and 83 shown in Fig. 1. Obviously the valve, by suitable piping connections may be mounted independently of the tank.

The valve housing II4 contains chamber 88 for connection to the pump inlet by pipe 8i and chamber II6 for connection to the pump discharge or high pressure side of pipe 80. It also contains low pressure chambers 89 and II8 each passing through the upper surface of the housing for connection to the tank as shown. Chambers I46 and I4! are connected respectively by pipes I20 and I2I to the upper and lower ends of hoist I25.

Manual control of the operation of the hoist is effected by appropriate movement of the cylindrical valve plunger I30 arranged in and passing through bore I3I in the housing. The ends of the plunger are fitted with stop flanges 532 and I33, one of which is positioned by means of the manipulative eye I34. The valve is shown in the neutral or hold position, which looks the hoist plunger wherever it may be positioned at the time, serving thereby to hold the bulldozer blade in a fixed position against dislodgement.

The valve plunger bore I3I is intersected in sequence by hoisting chamber I il, discharge passage I48, lowering chamber I40, pump discharge chamber and tank return chamber I I8 separated by appropriate walls. The plunger 136 is a cylindrical rod having a close fit in the bore by all portions of its surface not interrupted by ports or grooves. The full diameter portions are termed lands and there is one numbered I at the left end, one numbered I4I at the right end and three intermediate ones of various lengths. The surface of the plunger is provided with circumferential grooves I42, I43, I44 and I35 each of which has at least the function of spanning and thus connecting certain passages and chambers in the valve housing. The housing is equipped with a system relief valve I35 opening from pump discharge chamber IIG to tank connected chamber I I8 and fitted with adjusting means as shown.

The main valve plunger is drilled from the left end to provide a central passage or bore I ported at I5I to the groove I 44 and ported at 152 to the surface of the land intermediate grooves I42 and I43. A check valve I54 is spring pressed closed and prevents liquid movement from [52 toward I5I but not in the opposite direction. The spring chamber behind the valve is closed by plug I positioned by a screw portion I56 on flange I32. Proper venting of the plunger of the check valve, as shown, prevents fluid look.

When the valve is moved to the left from the neutral position shown, the land I4! closes the port between passages Hi5 and H8 so that the pressure fluid from the pump is no longer returned to the tank. This high pressure fluid now enters ports I5I by way of groove hi4, passes through passage I50, lifts check valve I52, flows out through ports I52 into passage I ll now registering therewith and passes to the underside of the piston of the hoist. Groove I43 has been moved to span passages I46 and I48 so that fluid returning from the upper side of the hoist by way of I46 is delivered into I48 to be returned to the tank.

.1 -When the plunger 30 ismoved a portion of the permitted ,distance toward the right from .the neutral position the land to the right of groove. I44 closes off communication between H6 and H8 andhigh pressurefiuid flows through check valve I54 to chamber I46 connectedto the upper sideof the. hoist. Grooye L42 .now spans hoist chamber I4] and passage 148' to discharge liquid from the under side of piston I216. In either of the-hoist or lowering operations when the piston reaches the end of its stroke, continued delivery of fluid by the constantly driven pump lifts relief valve 135. and returns the liquid toth tank.

Since in the closed system the pump inlet :is supplied from the discharge from the hoist, the discharge passage I148 is adapted to. be connected to either of the hoist passages I46 or I41 and delivers in a manner to be later described: to the low pressure outlet port 88 connected directly to the pump inlet. :Controlof .the delivery of fluid to the pump must be such that this system operates as an open system when the control valve is in the neutral or hold position illustrated, for then the pump .delivershigh pressure to I1 6 through the groove I39 inv the plunger into the low pressure discharge passage IIB back to the tank. The pump must then be able to take liquid from the tank for circulation to maintain adequate cooling during idling periods. For this purpose the low pressure chamber 89 forms an-extension to the passage I48 and has its'upper end open to the tank. Reciprocably mounted in this bore 89 is a valve member 99 comprising a close fitting cylindrical sleeve open at the ends and containing a central partition 91. Above the partition it is provided with lateral ports 92; below with corresponding lateral ports 93. The open bottom of this valve is arranged to receive return liquid from the hoist directly from :the passage I48 in accordance with the position of thecontrol valve.

With the flow controlvalveell inits lower position, as illustrated, fluid cannot escape through ports 93, which are closed off by walls of the bore in which th valve operates and the valve provides direct passage for liquid from the tank into the open upper end thereof and out through ports 92 into the low pressure passage 88 delivering to the pump. When the manual control valve plunger is set to move the hoist in either direction the discharge from the opposite 'end'of the latter coming from passage 146 or I4! is delivered from the appropriate groove'in the plunger into-discharge passage I48 and flows into lower side of the flow control valve 90, building up a pressure therein sufficient to lift the valve against the very small pressure produced by the head of the liquid in the tank. Upward movement of the valve is limited by the underside of the tank wall and under these conditions the return fluid from the hoist discharges through ports 93 to-88 and supplies the pump.

If the control valve is set to the raise posi- "tion the quantity of liquid being received from the upper portion of the hoist is less than that being delivered by the pump, because of the volume occupied by the piston rod. Under these conditions the pump inlet takes away liquid faster than it is being delivered throughports '93, thus reducing pressure on the underside of 'valve 90, permitting it to lower sufliciently to partially uncover ports 92, which-provide makeup liquid direct from the tank to-compensate for the difierential volume on the two sides of the hoist piston.

On the reverse operation, i. e., lowering of the Lhoist, more fluid is being delivered beneath the nowrelevated flow control valve 90 than is being :taken by the pump vfor-delivery to the'upper side em s. rrnisextra quantity of liquid builds up a pressure beneath valve: 90. which acts on low pressure relief valvetji through its passage 95., which is exposed when theskirtoi the flow control valve is lifted. This permits adequate fluid relief to the tank through passages 96 and 91;. The low pressure relief valve 86 is normally maintained closed by .a light adjustable spring, as shown.

It will be seen that th flow control valve automatically provides compensation. for the difference in volume of 'oil handled from thetwo sides of the hoist piston. It is. also responsible for transferring the system. from an open one when the control valve is in the neutral or hold position to a closed one when the hoist is. being operated. The operation of thev hoist by a closed system insures against the piston moving away from the body oi oil which is attempting to lower the load,v due to the latter trying to advance more rapidly, due to its weight, than the moving fluid. It is obvious that the tension on the springxcontrolling the low pressure relief valve 86 must be such that the hoist cannot fall of its: own accord but must be forced down by the delivery of a lesser quantity of fluid to the upper side of the piston. A few pounds difl'erential is adequate, which serves to relieve the pump of any substantial work during the lowering operation.

When the valve plunger I30 is pulled to its maximum position to the right, the float condition occurs, permitting the bulldozer blade to find its own level, and groove I44 spans passages H 6 and I I8 permitting the pump to freely deliver fluid to the tank. Groove I42 spans recesses I46, I41 and I48. This connects the hoist passages to each other so that the piston thereof is free to be moved under the action of its load'in either direction. Since there is a differentialthe volume of the two ends of the hoist cylinder the multiple longitudinal grooves I15 are provided at the right end of groove I43 and they serve to span passages I46 and H6. Oil may be taken from or delivered to this passage H6 in accordance with requirements from passag I46which is new connected to the other hoist passage I48.

The valve of Fig. 3 is a modification in form with substantially the same performance of that of Fig. 2. The valve body 3I4 has its ports and passages somewhat differently arranged from those just described; The high pressure liquid from the pump is delivered into chamber 316 with parallel branch intersecting the plunger bore on opposite sides of a partition 311 which closes ofi groove 344 and ports 35I when the plunger is in neutral position.

Although the plunger has a slightly different arrangementof grooves it has the same number as on the plunger'of Figure 2 and is equipped in an identical manner with a check valve.

In operation the neutral position of the valve provides the same performance as takes place in connection with Figure 2, fluid entering through 3.16, passing through groove 239 and back to the tank by way of Si 8 providing a freepassage of liquid between the pump andthetank. A high pressure relief valve which maybe similar or=identical in construction to that disclosed a-t I35 in Figure 2 is provided at 335 in a corresponding position with respect to the high pressure inlet ,from the pump and discharges into passage 31-3 for returning liquid to the tank.

The operation of the main control plunger will made to connect the joined hoist ports to the inlet chamber 3l6. The slightly different position of the pump inlet chamber 383 provides a convenient arrangement for the low pressure relief valve 386, between it and the return passage M8. The flow control valve 398 is similar to that in Fig 2 and functions the same except for the provision of bleed port 399 through partition 39| which provides the compensation for volume differential on the two sides of the hoist piston. This bleeder port may be relied upon to take care of the excess liquid from the larger volumed side of the hoist during normal operation and the relief valve 385 omitted.

In all of the valves it will be noted that the packing at the right hand end of the main control valve has interposed between it and any source of .high pressure fluid, a low pressure chamber which prevents putting this packing under any considerable pressure, and it is therefore insured against leakage. At the opposite end, however, the packing is closely adjacent the hoisting port, which at times is filled with high pressure liquid. Any seepage along the valve to the left hand packing is permitted to vent to the tank in Figure 2 through passage 14c connected to the pump inlet. A corresponding drain passage is provided in the construction of Fig. 3 to prevent high pressure liquid acting on the packings.

Each of the valves as just described provides for complete manual control of the hoist for operating a bulldozer or other device under all condi tions of lifting and lowering and positively insures against the hoist taking control away from the operator on the lowering operation and dropping at an undesired speed. The system provides for full circulation of the oil between the pump and the tank in the neutral position of the valve where it remains for the largest portion of time during the operation of any hydraulically controlled earth-moving equipment. Adequate cooling is thereby insured.

This application is a division of my copending application Serial No. 550,078, filed August 18, 1944, now Patent Number 2,477,669 granted Aug. 2, 1949.

I claim:

1. A control valve for use in a hydraulic system composed of a double acting hoist, a tank and a positive displacement pump, comprising a valve housing having a bore, a reciprocable plunger movable in said bore to raise, hold, lower and float positions, said plunger having lands and intermediate grooves, a longitudinal bore in said plunger connecting spaced ports through the plunger, a check valve in said plunger bore between-said ports, said housing having a plurality of passages intersecting said first bore for selective cooperation with said plunger grooves and ports, one of said passages being adapted for connection to the pump outlet, two of said passages being adapted respectively for connection to opposite ends of the hoist, a return fluid passage intermediate said hoist passages arranged to return fluid from the hoist for reuse by the pump, a pump inlet chamber, a connection between said chamber and the said return fluid passage, a valve in said connection adapted to be opened by fluid pressure in said return fluid passage, and a relief valve from said last mentioned passage to said tank operable when more liquid is returned than is required by the pump.

2. A control valve for use in a hydraulic system composed of a double acting hoist, a tank and a positive displacement pump, comprising a valve housing having a bore, a reciprocable plungermovable in said bore to raise, hold, lower and "float positions, said plunger having lands and intermediate grooves, a longitudinal bore in said plunger connecting spaced ports through the plunger, a check valve in said plunger bore between said ports, said housing having a plurality of passages intersecting said first bore for selective cooperation with said plunger grooves and ports, one of said passages being adapted for connection to the pump outlet, two of said passages being adapted respectivel for connection to opposite ends of th hoist, a return fluid passage intermediate said hoist passages arranged to return fluid from the hoist for reuse by the pump, a pump inlet chamber, a connection between said chamber and the said return fluid passage, a valve in said connection adapted to be opened by fluid pressure in said return fluid passage, said connection also leading to said tank and a second portion on said valve regulating the flow between the tank and said chamber whereby the pump demands are satisfied from the return fluid augmented by that from the tank when necessary.

3. A control valve for use in a hydraulic system composed of a double acting hoist, a tank and a positive displacement pump, comprising a valve housing having a bore, a reciprocable plunger movable in said bore to raise, hold, lower and float positions, said plunger having lands and intermediate grooves, a longitudinal bore in said plunger connecting spaced ports through the plunger, a check valve in said plunger bore between said ports, said housing having a plurality of passages intersecting said first bore for selective cooperation with said plunger grooves and ports, one of said passages being adapted for connection to the pump outlet, two of said passages being adapted respectively for connection to opposite ends of the hoist, a return fluid passage intermediate said hoist passages arranged to return fluid from the hoist for reuse by the pump, a pump inlet chamber, a connection between said chamber and the said return fluid passage, a valve in said connection adapted to be opened by fluid pressure in said return fluid passage, said connection also leading to said tank, a second portion on said valve regulating the flow between the tank and said chamber whereby the pump demands are satisfied from the return fluid augmented by that from the tank when necessary, and means to waste return fluid to the tank when it is in excess of the pump demand.

4. A control valve for use in a hydraulic sys. tem composed of a double acting hoist, a tank and a positive displacement pump, comprising a valve housing having a bore, a reciprocable plunger movable in said bore to raise, hold, lower and float positions, said plunger having lands and intermediate grooves, a longitudinal bore in said plunger connecting spaced ports through the plunger, said housing having in the following order passages intersecting said first bore for selective cooperation with said plunger grooves and ports; first hoist passage, return fluid passage, second hoist passage, pump discharge passage and tank delivery passage; said lands in the neutral position of the plunger being positioned to isolate the hoist passages and one of said grooves being positioned to connect the pump discharge and tank delivery passages; one set of said ports being so positioned as to open selectively into the hoist passages when the plunger is moved from neutral, the other set of ports being arranged for positioning in the pump discharge passage;

lands arranged to separate the pump discharge and tank delivery passages when the first set of ports is positioned in either hoist passage; a bore communicating at one end with said tank, at the opposite end with said return fluid passage, a pump inlet chamber having a passage into said last mentioned bore and a valve element reciprocable in said last mentioned bore under the differential of tank and return liquid pressures and arranged to connect said last passage selectively to the tank and the return fluid passage.

5. The control valve as defined in claim 4 in which said valve element reciprocable in the bore between the tank and return fluid passage is arranged to connect the said pump inlet chamber simultaneously to the tank and return fluid passage to compensate for unequal displacements at the two ends of the hoist.

6. A control valve for a hydraulic system composed of double acting hoist, tank and constant running positive displacement pump, comprising a valve housing having a bore, a plunger reciprocable in said bore and having lands, circumferential grooves and longitudinally spaced ports, a longitudinal bore connecting said ports, said bore intersecting a single pump discharge REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,362,671 Schwan Nov. 14, 1944 2,392,422 Stephens Jan. 8, 1946 2,448,532 Kirkham Sept. '7, 1948